Statistics in a Nutshell

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Statistics in a Nutshell

• Interested in Entire Population
• Large Population Expensive Surveys
• Sample a Small Group
• Infer Population Characteristics
• from Sample Characteristics

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Examples

• Exit polls on election day
• Marketing surveys for new products
• Medical trials for new vaccines
• Neilson ratings of television shows
• Air measurements for pollutants

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Definitions

• Population --- Universe (Entire Group)
• Parameter
• Numeric Characteristic of a Population
• Average, Variance, Standard Deviation, etc
• Sample --- Subgroup of the Population
• Statistic
• Numeric Characteristic of a Sample
• Average, Variance, Standard Deviation, etc

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Sampling

• Sampling is faster, cheaper, easier.

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Sampling

• Sampling is faster, cheaper, easier.
• Hope, that the sample is representative of the
• population and therefore, the sample statistic
• is an accurate estimate of the population
• parameter.

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Sampling

• Sampling is faster, cheaper, easier.
• Hope, that the sample is representative of the
• population and therefore, the sample statistic
• is an accurate estimate of the population
• parameter.
• If the sample is not representative of the
• population, then all bets are off !

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Statistics

• Descriptive Statistics
• Collecting and Analyzing Data
• Tells a story about the numbers
• Inferential Statistics
• Drawing conclusions about a population

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Descriptive Statistics

• Measures of Central tendency
• Mean (Arithmetic Average)
• Median (Middle Value)
• Measures of Variation
• Variance
• Standard Deviation

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Measures of Central Tendency

• Mean
• Arithmetic Average
• Balance Point
• Basis for other statistics
• Influenced by extremes
• Median
• Middle Value
• Different Balance Point
• Not influenced by extremes

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Important Statistics

• Mean
• Tells where the data is centered
• Standard Deviation
• Tells how far the data is spread out

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Family Reunion

• Babies, youngsters, teenagers
• young adults, middle-aged parents
• grandparents, great grandparents
• Average Age ?????
• Standard Deviation ?????

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15th High School Reunion

• Average Age ?????
• Standard Deviation ?????